Sintered bearings have been widely used as bearings for a small precision motor by virtue of their excellent quietness. The sintered bearings are roughly divided into a copper-based sintered bearing mainly formed of copper, an iron-based sintered bearing mainly formed of iron, and a copper-iron-based sintered bearing mainly formed of copper and iron. A sintered bearing of any of those types is generally used after pores of its porous structure are impregnated with lubricating oil. For example, as a copper-iron-based sintered bearing impregnated with lubricating oil, there is known a sintered bearing obtained by using copper-based powder having a diameter of 45 μm or less, in which a ratio of copper and oil permeability are each specified within a predetermined range (see Patent Literature 1).